A tilt-type steering apparatus is widely known. First, a first conventional example of a vehicle steering apparatus will be described based on the disclosure of Patent Document 1. As shown in FIG. 7, a vehicle steering apparatus is configured such that rotation of a steering wheel 1 is transmitted to an input shaft 3 of a steering gear unit 2, a pair of left and right tie-rods 4, 4 is pushed/pulled in connection with rotation of the input shaft 3 and a steering angle is thus applied to front wheels. The steering wheel 1 is supported and fixed to a rear end portion of a steering shaft 5. The steering shaft 5 is rotatably supported by a cylindrical steering column 6 with being axially inserted into the steering column 6. A front end portion of the steering shaft 5 is coupled to a rear end portion of an intermediate shaft 8 via a universal joint 7. A front end portion of the intermediate shaft 8 is coupled to the input shaft 3 via a separate universal joint 9. The shown example is configured as an electrically-operated power steering apparatus. A front end portion of the steering column 6 is provided with an electric motor 10 that is a driving source for applying an auxiliary force and a housing 11 that is fixed to the front end portion of the steering column 6. The electric motor 10 is supported by the housing 11. Output torque (auxiliary force) of the electric motor 10 is applied to the steering shaft 5 through a gear unit and the like provided in the housing 11.
An upper-front end portion of the housing 111 is supported in a tiltable manner with respect to a vehicle body 12 by a tilt shaft 13 arranged in a width direction. A support bracket 14 supported by the vehicle body 12 is mounted to a rear end-slanted part of the intermediate portion of the steering column 6. The support bracket 14 has a pair of support plate portions 15 spaced in the width direction. The support bracket 14 is supported by the vehicle body 12 in a state in which the support plate portions 15 hold the intermediate portion of the steering column 6 from both sides thereof in the width direction. A lower part of the intermediate portion of the steering column 6 clamped by the support plate portions 15 is provided with a displacement bracket 16 (an example of a clamped portion). In the specification, the “width direction” means a width direction of the vehicle body on which the steering apparatus is mounted, and a “front-rear direction” means a front-rear direction of the vehicle body. The “intermediate portion” is a part other than both ends and may include a part near one end or both ends.
Each support plate portion 15 is formed with an up-down slot 17 having an arc shape about the tilt shaft 13 or a linear shape along a tangential line direction of the arc shape and is elongated in an up-down direction. A portion of the displacement bracket 16 aligned with a portion of the slot 17, is formed with a through-hole 18. The structure shown in FIG. 7 is provided with a tilt-telescopic mechanism configured to adjust not only a height position of the steering wheel 1 but also a front-rear position of the steering wheel 1. The through-hole 18 is formed as a front-rear slot elongated in an axial direction of the steering shaft 5 and the steering column 6. In conformity to this, the steering shaft 5 and the steering column 6 are configured in a telescopic manner. A tilt rod is inserted in the slot 17 and the through-hole 18 in the width direction. One end portion of the tilt rod is provided with a tilt lever and the other end portion is provided with an anchor part, thereby forming a tilt lock mechanism for widening and narrowing a gap between the inner surfaces of the support plate portions 15 based on a rotation of the tilt lever. When positioning the steering wheel 1, the tilt lever is rotated in a predetermined direction, so that the gap between the inner surfaces of the support plate portions 15 is widened. In this state, the height and front-rear positions of the steering wheel 1 can be adjusted within a range in which the tilt rod can be moved in the slot 17 and the through-hole 18. After moving the steering wheel 1 to a desired position, when the tilt lever is rotated in a reverse direction to thus narrow the gap between the inner surfaces of the support plate portions 15, the steering wheel 1 can be kept at an adjusted position.
As a more specific structure of the tilt-type steering apparatus, Patent Document 1 also discloses a structure shown in FIGS. 8 to 11. This second conventional example also has a telescopic mechanism configured to adjust the front-rear position of the steering wheel 1, in addition to the tilt mechanism configured to adjust the height position of the steering wheel 1 (see FIG. 7). A steering column 6a of the second conventional example has a rear-side outer column 19 and a front-side inner column 20. A front end portion of the outer column 19 and a rear end of the inner column 20 are fitted in an axially movable manner, so that an entire length of the steering column 6a can be extended or shortened. The front end portion of the outer column 19 has a notched cylindrical shape, so that a diameter of the front end portion of the outer column 19 can be expanded and reduced. By adjusting a force holding the front end portion of the outer column 19 from both sides thereof in the width direction, an inner diameter of the front end portion of the outer column 19 can be expanded or reduced. A steering shaft 5a is supported radially inside the steering column 6a in a rotatable manner. The steering shaft 5a is also configured such that an entire length of the steering shaft 5a can be extended or shortened by a combination of an outer shaft 21 and an inner shaft 22.
A housing 11a for mounting components of the electrically-operated power steering apparatus, such as an electric motor 10a (see FIG. 11), a decelerator and the like, is connected and fixed to a front end portion of the steering column 6a. The housing 11a is supported in a tiltable manner at a portion of the vehicle body by a tilt shaft (bolt) inserted into a support pipe 23 provided widthwise at an upper part of the housing 11a. The steering wheel 1 is fixed to a rear end portion of the steering shaft 5a more protruding rearwards than the steering column 6a. A front end portion of the steering shaft 5a more protruding forwards than the steering column 6a is coupled to an intermediate shaft 8 (see FIG. 7) via the universal joint 7.
A support bracket 14a is connected to and supported by a vehicle body-side bracket (not shown) fixed to the vehicle body such that it can be displaced (separated) forward by a impact load based on a secondary collision. The support bracket 14a has an attachment plate part 24 and a pair of left and right support plate portions 15a. 15b, which are made of metal plate materials having sufficient strength and stiffness, such as steel plates. The attachment plate part 24 and the support plate portions 15a, 15b are connected and fixed by welding and the like. The attachment plate part 24 is supported by the vehicle body so that it can be separated forward based on the impact load applied due to the secondary collision.
The support plate portions 15a, 15b are provided to clamp the outer column 19 from both sides thereof. At locations on the support plate portions 15a, 15b that are aligned with each other, arc-shaped up-down slots 17 (partially shown in FIG. 8) having a central axis of the support pipe 23 as a center are formed. The outer column 19 is supported between the support plate portions 15a, 15b by a tilt rod 25 inserted into the up-down slots 17. A front-upper part of the outer column 19 is provided with a clamped portion 27 having a pair of supported wall portions 26, 26, which are widthwise spaced from each other. The respective supported wall portions 26, 26 are formed with front-rear slots 28 (through-holes, see FIG. 9) which are elongated in the axial direction of the outer column 19. The outer column 19 is supported with respect to the support bracket 14a by the tilt rod 25 inserted into the up-down slots 17 and the front-rear slots 28. Therefore, the outer column 19 can be tilted in the up-down direction about the bolt inserted into the support pipe 23 within a range in which the tilt rod 25 can move inside the up-down slots 17. Furthermore, the outer column 19 is movable in the front-rear direction (axial direction) within a range in which the tilt rod 25 can move inside the front-rear slots 28.
The tilt rod 25 has one end portion (a right end portion of FIG. 11) to which an outward flange-shaped collar part 29 (an anchor part) is fixed and the other end portion to which a can device 32 having a driving cam 30 a driven cam 31 is provided. When the driving cam 30 is rotated by a tilt lever 33, a distance between the driven cam 31 and the collar part 29 can be widened or shortened. Opposing surfaces of the driving cam 30 and the driven cam 31 are respectively formed with cam surfaces on which concave portions and convex portions are alternately arranged via inclined surfaces (see, e.g., Patent Document 2). The cam device 32 is configured such that an axial size of the cam device 32 is expanded with the convex portions being butted to each other and the axial size of the camn device 32 is reduced with the convex portions being fitted to the concave portions of the counterpart side surface. The driving cam 30 is connected to a base end part of the tilt lever 33 in a fixed manner. The driven cam 31 is engaged with the up-down slot 17 formed at one (the left support plate portion 15a) of the support plate portions 15a, 15b such that it is movable only along the up-down slot 17 (with the rotation about the tilt rod 25 being blocked).
When positioning the steering wheel 1, the tilt lever 33 is rotated downward to reduce the axial size of the cam device 32 and to expand the distance between the driven cam 31 and the collar part 29. As a result, the distance between the inner surfaces of the support plate portions 15a, 15b is increased and a surface pressure between the inner surfaces of the support plate portions 15a, 15b and the outer surfaces of the supported wall portions 26, 26 is lowered or lost. In this state, since the supporting force of the clamped portion 27 with respect to the support bracket 14a is lowered or lost, the outer column 19 is moved within the range in which the tilt rod 25 is movable inside the up-down slots 17 and the front-rear slots 28. By this movement, the position (one or both of the height position and the front-rear position) of the steering wheel 1, which is supported by and fixed to the rear end portion of the steering shaft 5a rotatably supported in the outer column 19, is adjusted.
After positioning the steering wheel 1, the tilt lever 33 is rotated upward to expand the axis size of the cam device 32 and to shorten the distance between the driven cam 31 and the collar part 29. As a result, the inner surfaces of the support plate portions 15a, 15b and the outer surfaces of the supported wall portions 26, 26 are strongly contacted to each other, so that the height position of the steering wheel 1 is fixed. At the same time, the diameter of the front end portion of the outer column 19, to which the supported wall portions 26, 26 are provided, is reduced and an inner periphery of the front end portion of the outer column 19 and an outer periphery of the rear end portion of the inner column 20 are strongly contacted to each other, so that the steering column 6a cannot be extended or shortened. As a result, the front-rear position of the steering wheel 1 is fixed.
In the tilt-type steering apparatus having the cam device 32 as the engaging mechanism, as described above, a rotation amount of the tilt lever 33 is suppressed to be smaller, compared to a tilt-type steering apparatus having a screw-type mechanism having a nut and a bolt (stud) as the engaging mechanism, so that the high engaging force is obtained. However, as the cam device 32 is used, when the tilt lever 33 is rotated in a predetermined direction (for example, a downward direction) so as to position the steering wheel 1, the tilt lever 33 may be excessively rapidly rotated. The reason is that when the tilt lever 33 is rotated in the predetermined direction to thus move the respective convex portions towards the concave portions of the counterpart side surface from the state where the convex portions of the cam surfaces of the cams 30, 31 are butted to each other, the respective convex portions are moved to slide down along the inclined surfaces of the counterpart side cam surface. That is, in a state in which the position of the steering wheel 1 is fixed, a force is applied between the cams 30, 31 in a direction of separating the cams from each other. From this state, when moving the respective convex portions of the cam surfaces of the cams 30, 31 towards the concave portions of the counterpart side cam surface, the respective convex portions are rapidly moved towards the respective concave portions along the inclined surface of the other side cam surface. In other words, the respective convex portions are moved to slide down along the respective inclined surfaces towards the respective concave portions. As a result, the tilt lever 33 having the base end part to which the driving cam 30 is fixed is rapidly rotated in the predetermined direction, so that a driver operating the tilt lever 33 may feel uncomfortable or unpleasant, or an unpleasant collision noise may be generated.